The αɛθ core ofEscherichia coliDNA polymerase III (Pol III) associates with the β2sliding clamp to processively synthesize DNA and remove misincorporated nucleotides. The α subunit is the polymerase while ɛ is the 3′ to 5′ proofreading exonuclease. In contrast to the polymerase activity of Pol III, dynamic features of proofreading are poorly understood. We used single-molecule assays to determine the excision rate and processivity of the β2-associated Pol III core, and observed that both properties are enhanced by mutational strengthening of the interaction between ɛ and β2. Thus, the ɛ-β2contact is maintained in both the synthesis and proofreading modes. Remarkably, single-molecule real-time fluorescence imaging revealed the dynamics of transfer of primer-template DNA between the polymerase and proofreading sites, showing that it does not involve breaking of the physical interaction between ɛ and β2.

中文翻译：

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大肠杆菌Pol III复制酶的校对动力学

大肠杆菌DNA聚合酶III（Pol III）的αɛθ核心与β2滑动钳结合，以合成DNA并去除错误掺入的核苷酸。α亚基是聚合酶，而ɛ是3'至5'校对核酸外切酶。与Pol III的聚合酶活性相反，对校对的动态特征了解得很少。我们使用单分子测定法来确定与β2相关的Pol III核心的切除率和合成能力，并观察到通过strengthening和β2之间相互作用的突变增强，两种性质都得到了增强。因此，在合成和校对模式下都保持了both-β2接触。值得注意的是，单分子实时荧光成像揭示了引物模板DNA在聚合酶和校对位之间转移的动力学，